If a solution changes from pH 4 to pH 7, what happens to hydrogen ion concentration?
Answer and explanation
Correct answer: It decreases one thousand times
The pH relationship is pH = −log[H⁺], so every increase of one pH unit represents a tenfold decrease in hydrogen-ion concentration. The change from pH 4 to pH 7 is three units; therefore the concentration changes by 10³ = 1000 in the decreasing direction. Hence option A is correct, not B, which treats the pH difference as an ordinary multiplier.
Frequently asked questions
What is the correct answer to this question?
It decreases one thousand times
Why is this the correct answer?
The pH relationship is pH = −log[H⁺], so every increase of one pH unit represents a tenfold decrease in hydrogen-ion concentration. The change from pH 4 to pH 7 is three units; therefore the concentration changes by 10³ = 1000 in the decreasing direction. Hence option A is correct, not B, which treats the pH difference as an ordinary multiplier.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
